The present invention relates to a disk device, and more particularly to an actuator control device for driving a head having at least a function of reading information.
A typical conventional disk storage device has been disclosed in JP-A-6-267211.
This disk storage device includes a first correcting unit for adding a first disturbance compensating signal for canceling disturbance into an input signal of a driving circuit for correcting the input signal, a storage unit for storing the first disturbance compensating signal and outputting it, a second correcting unit for adding a second disturbance compensating signal for canceling the disturbance left out of the previous compensation into a position compensating signal for correcting the position compensating signal, an estimating unit for estimating the second disturbance compensating signal, and a disturbance compensating signal modifying unit for storing an added signal of the first and the second disturbance compensating signals as a new first disturbance compensating signal in the storage unit. This disk storage device arranged as above is served to cancel the adverse effect on the positioning control system by disturbance or vibrations. Hence, the provision of the disk storage device makes it possible to improve the positioning accuracy and shorten the access time.
The conventional disk storage device as disclosed in JP-A-6-267211, however, does not provide the following capability. If such external force like an external shock as exceeding the maximum force generated by an actuator (referred to as the maximum generation of the actuator) is applied to the apparatus provided with the actuator so that its tracking control is lost (referred to as xe2x80x9cout of trackxe2x80x9d or xe2x80x9cout of trackingxe2x80x9d), it is highly likely that the conventional device may continue to move the head over the tracks in the xe2x80x9cout of trackingxe2x80x9d state, making it impossible to restore the tracking control state.
This is because the position error signal gets out of a controllable feedback area so that the signal may be in reverse polarity to that of the positive feedback area and thus a disturbance estimating operation by a disturbance observer may be made divergent.
It is an object of the present invention to provide an actuator control device which may provide a capability of performing such a modification as making an output of the disturbance observer zero and quickly returning to the tracking control state if the external force like an external shock exceeding the maximum generation of the actuator may be applied to the device itself or the xe2x80x9cout of trackingxe2x80x9d takes place.
According to an aspect of the invention, the actuator control device includes a head for recording and reproducing information on and from a disk, one or more actuators for moving the head, a position detector for defecting a position of the head, a control unit for controlling the actuator based on the position of the head, a disturbance observer for estimating a disturbance amount added to the actuator, a storage unit for storing the estimated disturbance, an adding unit for adding an output of the disturbance observer and an output of the storage unit to an output of the control unit, and a driving circuit for driving the actuator on the basis of the output of the adding unit. The actuator control device is further equipped with an abnormality detector for detecting an application of an external shock to the device on the basis of the position of the head and the output of the disturbance observer and a modifying unit for modifying an output of the disturbance observer according to the output of the abnormality detector, for the purpose of modifying the output of the disturbance observer if external force like an external shock exceeding the maximum generation of the actuator is applied to the device itself.
As the abnormality detector, a feedback area detector is provided for detecting a positive feedback area and a negative feedback area of the head position and for modifying the output of the disturbance observer according to the output of the feedback area detector.
Further, as the abnormality detector, a vibration detector is provided for detecting vibrations added to the device itself through the use of an accelerometer and a vibrometer provided in the detector itself.